Home' Asia Pacific Defence Reporter : APDR_MAY_2011_HighRes.pdf Contents 26 | Asia Pacific Defence Reporter
26 | Asia Pacific Defence Reporter
A submarine’s endurance is defined as “the
number of days the boat can remain at sea
unsupported” Factors effecting this are:.
Fuel load is a primary contributor to the period
of time a submarine can spend at sea. If one
discounts leaving harbour with a full battery and
returning with it fully discharged, the total energy
requirement of a submarine, the combined
mission hotel and propulsion load, has to be met
by the carriage of fuel, including that used for Air
Independent Propulsion (AIP).
Clearly the propulsion load has an effect on the
usage rate for fuel.
HULL AND EQUIPMENT EFFICIENCIES
Efficiencies in a submarine’s hull design and
equipment affect submarine endurance.
A decrease in hull size for a given capability
represents an efficiency that will improve
endurance. Flowing from that, technological
advances that reduce equipment sizes and
weights without reducing capability are generally
welcomed by submarine designers. They allow for
smaller hull sizes and simplify equipment layout.
Hull shapes optimised to reduce hull form drag
and the use of specialized hull materials or paints
which help reduce skin friction and can also affect
The selection of highly efficient equipment
such as permanent magnetic motors, highly
efficient diesel engines and generators, efficient
static inverters for power conversion and low
voltage technology in platform and mission
system electronic systems all serve to reduce
energy consumption throughout a patrol.
Modern technology also allows for the removal
of a number of energy and space consuming
components. For example, lithium ion batteries
eliminate the need for battery ventilation, cooling
and hydrogen elimination systems. Automation
and the shift to totally integrated platform
monitoring and control systems helps reduce
the number of watch keepers required, thereby
minimising crew numbers which in turn assists
in reducing submarine size requirements and
reducing hotel loads.
RELIABILITY, MAINTAINABILITY AND
Reliability is a function of equipment selection
and design, age and usage rates, maintenance
philosophies and maintenance scheduling.
Failure of critical systems due to normal wear and
tear or battle damage and subsequent non repair
can terminate a patrol as will the accumulation
of failures and non-repair of less critical systems.
Unlike fuel, reliability cannot be reset by
pulling up alongside a support base or tender.
Compounding the problem, the reliability clock
starts ticking as soon as equipment is switched on
after the last major overhaul.
The ability to effect onboard repairs in the
event of equipment failure is also an important
consideration; an ability influenced by the
capabilities of monitoring systems and diagnostic
tools, the level of technical and maintenance
documentation available, the competency of
maintenance staff and the availability of the
Available stowage space for spares, consumables
and food can affect submarine endurance.
Refrigerated stowage space can be a particularly
limiting factor. Whilst space can be found for
additional patrol supplies, if required, this is not
true for perishable items.
The storage capacity for potable water can also
constrain endurance if fresh water generation is
not a possibility.
Crew endurance is an input to overall submarine
endurance with the provision of space, amenities
and facilities helpful in maintaining crew moral.
Improving space for crews can be achieved by
automation, which in turn can reduce crew size
requirements and associated food and other
stowage space requirements.
Payload capacities, which are traditionally limited
on submarines, can have an effect on “mission
endurance”. Once a submarine has used all of
its effectors, be they torpedoes, missiles, mines
or the deployment of Special Forces, the mission
will end. Specific tasking, such as land strike
or mine laying, where a large percentage of the
total payload is consumed in a single event, can
shorten mission endurance. The situation is
worsened by the fact that there is now a greater
variety of effectors that can be embarked. During
high intensity conflicts where a variety of effector
types are loaded for mission flexibility reasons,
it may be possible to consume all embarked
torpedoes after encounters with only a few enemy
Before moving off the topic of endurance, it is
worth explicitly pointing out that hull size does
A range of submarine options
Last month the generic roles and functions of a submarine were mapped into the Australian context and some analysis was carried out to identify
any aspects of the Australian requirement that stood out as unique.
One requirement that warranted further discussion was that of submarine “endurance” and “range”. It was acknowledged, and is largely
undisputed in military circles, that the Area of Operations (AO) for Australia’s future submarines will be both large and distant.
Are the Australian range and endurance requirement unique, or perhaps just unusual? Can the Australian requirement be met by a Military Off
The Shelf (MOTS) submarine, and if not, by how much does a MOTS submarine miss the mark? Finally, if the MOTS submarine does miss the mark,
how can the requirement gap be met economically by alternative solutions?
There is little point in procuring a future submarine that cannot meet ADF peace and wartime endurance and range needs. However, noting
the high cost that would be borne by the taxpayer for the procurement of a unique submarine design and the national consequences if any of the
significant own design project risks are realised, all options with respect to meeting endurance and range requirements must be considered.
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